How Many Imputations are Really Needed? Some Practical Clarifications of Multiple Imputation Theory

Multiple imputation (MI) and full information maximum likelihood (FIML) are the two most common approaches to missing data analysis. In theory, MI and FIML are equivalent when identical models are tested using the same variables, and when m, the number of imputations performed with MI, approaches infinity. However, it is important to know how many imputations are necessary before MI and FIML are sufficiently equivalent in ways that are important to prevention scientists. MI theory suggests that small values of m, even on the order of three to five imputations, yield excellent results. Previous guidelines for sufficient m are based on relative efficiency, which involves the fraction of missing information (γ) for the parameter being estimated, and m. In the present study, we used a Monte Carlo simulation to test MI models across several scenarios in which γ and m were varied. Standard errors and p-values for the regression coefficient of interest varied as a function of m, but not at the same rate as relative efficiency. Most importantly, statistical power for small effect sizes diminished as m became smaller, and the rate of this power falloff was much greater than predicted by changes in relative efficiency. Based our findings, we recommend that researchers using MI should perform many more imputations than previously considered sufficient. These recommendations are based on γ, and take into consideration one’s tolerance for a preventable power falloff (compared to FIML) due to using too few imputations.     

确保信息系统新项目成功实施的关键问题分析

叙述了从信息保障部门考虑,医院信息系统新项目实施过程中需注意的问题;应用项目管理的方法可有效解决这些影响项目实施成败的关键问题;指出医院信息保障部门对项目管理的积极参与,能够有效促进系统顺利实施.     

智慧医院互联网化服务设计与应用研究

以北京大学第三医院互联网诊疗服务应用为例,介绍智慧医院互联网化服务体系与安全体系设计以及具体应用实践,阐述智慧医院互联网诊疗服务构建策略.     

Cost-effectiveness analysis of a multinational RCT with a binary measure of effectiveness and an interacting covariate

In a recent multinational randomized clinical trial, 1356 patients from 14 countries were randomized between two arms. The primary measure of effectiveness was 30-day survival. Health care utilization was collected on all patients and was combined with a single country's price weights to provide patient-level cost data. The purpose of this paper is to report the results of the cost-effectiveness analysis for the country that provided the cost weights, so as to provide a case study for illustrating recently proposed methodologies that account for skewed cost data, the between-country variation in treatment effects, possible interactions between treatment and baseline covariates, and the difficulty of estimated adjusted risk differences. A hierarchal model is used to account for the two sources of variation (between country and between patients, within a country). The model, which uses gamma distributions for cost data and recent methods for estimating adjusted risk differences, provides overall and country-specific estimates of treatment effects. Model estimation is facilitated by Markov chain Monte Carlo methods using the WinBUGS software. In addition, the theory of expected value of information is used to determine if the data provided by the trial are sufficient for decision making.     

Investigation of Adhesion Properties of Tire—Asphalt Pavement Interface Considering Hydrodynamic Lubrication Action of Water Film on Road Surface

To obtain the tire–pavement peak adhesion coefficient under different road states, a field measurement and FE simulation were combined to analyze the tire–pavement adhesion characteristics in this study. According to the identified texture information, the power spectral distribution of the road surface was obtained using the MATLAB Program, and a novel tire hydroplaning FE model coupled with a textured pavement model was established in ABAQUS. Experimental results show that here exists an “anti-skid noncontribution area” for the insulation and lubrication of the water film. Driving at the limit speed of 120 km/h, the critical water film thickness for the three typical asphalt pavements during hydroplaning was as follows: AC pavement, 0.56 mm; SMA pavement, 0.76 mm; OGFC pavement, 1.5 mm. The road state could be divided into four parts dry state, wet sate, lubricated state, and ponding state. Under the dry road state, when the slip rate was around 15%, the adhesion coefficient reached the peak value, i.e., around 11.5% for the wet road state. The peak adhesion coefficient for the different asphalt pavements was in the order OGFC > SMA > AC. This study can provide a theoretical reference for explaining the tire–pavement interactions and improving vehicle brake system performance.     

Using measures of reading time regularity (RTR) to quantify eye movement dynamics,and how they are shaped by linguistic information

In this article, we present the concept of reading time regularity (RTR) as a measure to capture reading process dynamics. The first study is concerned with examining one of the assumptions of RTR, namely, that process measures of reading, such as eye movement fluctuations and fixation durations, exhibit higher regularity when contingent on sequentially structured information, such as texts. To test this, eye movements of 26 German native speakers were recorded during reading-unrelated and reading-related tasks. To analyze the data, we used recurrence quantification analysis and sample entropy analysis to quantify the degree of temporal structure in time series of gaze steps and fixation durations. The results showed that eye movements become more regular in reading compared to nonreading conditions. These effects were most prominent when calculated on the basis of gaze step data. In a second study, eye movements of 27 native speakers of German were recorded for five conditions with increasing linguistic information. The results replicate the findings of the first study, verifying that these effects are not due to mere differences in task instructions between conditions. Implications for the concept of RTR and for future studies using these metrics in reading research are discussed.     

国有医疗机构的产权特征、存在问题与改革

该应用现代产权经济学理论，结合医疗服务市场的特点，分析国有医疗机构的产权特征和存在问题，并探讨其改革思路。     

Routine Health Information Utilization and Associated Factors among Health Professionals Working in Public Health Facilities of the South Region,Ethiopia

BackgroundRoutine health information is the pillar for planning and management of health services and plays a vital role in effective and efficient health service delivery, decision making, and the improvement of programs. Therefore, this study aimed to assess routine health information utilization and associated factors among health professionals working in public health facilities of the south region.MethodsInstitution based cross-sectional study design was employed. Data was collected from randomly selected 719 participants using a pre-tested, interviewer administered structured questionnaire. Bivariate and multivariate logistic regression analyses were carried out.ResultThe overall utilization of routine health information was 63.1. Place of residence, HMIS personnel, HMIS code, overwhelming data source, population based data, data quality control, feedback, monitoring chart, 8.467) and data transfer policy were factors significantly associated with utilization of routine health information.ConclusionSix out of ten health professionals had utilized routine health information. Place of residence, HMIS personnel, HMIS code, overwhelming data source, population based data, data quality control, feedback, monitoring chart and data transfer policy had significant associations with routine health information utilization. Therefore, concerned health authorities need to work on these factors to improve the utilization.